1. Field of the Invention
The present invention is utilized in an accelerator controller of an automobile equipped with an internal combustion engine. The present invention relates to a control system including a program control circuit provided in a circuit for converting an operating amount of an accelerator pedal operated by a driver into an electric signal and transmitting the electric signal to an actuator for controlling an accelerator opening of an engine. Although the accelerator controller of the present invention is developed for use in a vehicle equipped with a diesel engine, it can be generally applied to an engine utilizing liquid fuel. The present invention relates to an improvement of an auto-cruising device. The present invention relates to an improvement of fuel consumption rate and an improvement of exhaust gas.
2. Description of Related Art
Auto-cruising devices are popularly used in automobiles. Most of auto-cruising devices are automatic control devices each of which is made active when a driver of a vehicle manually operates an actuation switch, sets a vehicle speed at the time of the operation of the actuation switch as an aimed speed and automatically controls an accelerator opening of an engine of the vehicle such that a vehicle speed is continuously kept at the aimed speed. When the auto-cruising device is effectively operating, it is possible to run the vehicle at a certain constant speed even when the driver releases an accelerator pedal. Such auto-cruising device is widely utilized in long distance running or other running at a certain constant speed.
In such conventional auto-cruising device, the auto-cruising control can be made inactive when a driver turns the actuation switch off, steps a brake pedal or shifts down a transmission gear. Further, the auto-cruising device is usually constructed such that, when a driver steps the accelerator pedal abruptly in the state where the auto-cruising device is effectively operating, the vehicle can be accelerated overriding the control of the auto-cruising device. When the actuation switch for auto-cruising includes a switch for changing an aimed vehicle speed, it is possible to accelerate or decelerate the vehicle by changing the aimed speed by the aimed speed changing switch even when the driver releases the accelerator pedal.
In most of such conventional auto-cruising devices, when a driver changes the aimed vehicle speed while the auto-cruising device is operating effectively, acceleration or deceleration control is executed such that the vehicle speed becomes a new aimed speed smoothly. JP2000-043611A discloses a technique in which, in a case where an acceleration or deceleration control is performed when a driver changes an aimed vehicle speed, a control gain is changed correspondingly to a vehicle speed at the aimed speed changing time. The object and the effect of the invention disclosed in JP2000-043611A is to improve the controllability of a vehicle. That is, the technique disclosed therein utilizes a feed-back control or a feed-forward control such that, when an aimed speed in an automatic control is changed stepwise, the vehicle speed approaches a new aimed speed as smoothly as possible without overshooting or control delay.
In the conventional auto-cruising device, the control is started by the manual operation of the driver, as mentioned above. According to an investigation made by the inventors of this application, it has been found that there is no auto-cruising device in which a cruising control is started automatically without requiring any manual operation of a driver when a constant condition is established. Further, a driver utilizes the conventional auto-cruising device by basically releasing an accelerator pedal when the auto-cruising control is started. Although there is the technique for overriding the control after the control is started, a technical thought that a control function for controlling an accelerator of a vehicle engine is changed in any way according to a displacement amount of the accelerator pedal is not known so far.
On the other hand, an improvement of the fuel consumption rate (distance covered by unit amount of fuel) is highly requested by vehicle users. Particularly, for commercial vehicle such as truck or bus, the fuel consumption rate is a very important factor for user in selecting the kind of vehicle. Further, in order to solve the recent environmental contamination problem due to exhaust gas, a further reduction of sulfur content of fuel for diesel engine has been considered. In order to reduce sulfur content of fuel for diesel engine, an additional step for refining the fuel is required in the oil refining process, causing fuel cost to be increased. Therefore, it is anticipated that the improvement of fuel consumption rate of vehicle becomes more and more important.
In order to effectively improve the fuel consumption rate, the present inventors paid an attention to a sudden acceleration of vehicle among various traveling resistances occurring in a vehicle, which increases fuel consumption. That is, when the traveling resistance of vehicle is classified to air resistance, rolling friction of wheels, acceleration resistance and grade resistance, etc., and a quantitative distribution of these resistive components is considered, it is clear that the traveling resistance, which can be controlled according to the driving mode, is the acceleration resistance. In order to reduce an influence of the acceleration resistance, it is preferable that, when a new aimed speed is set, a fuel supply control is performed such that a practical speed of a vehicle approaches gently and reasonably to the new aimed speed. That is, it is effective to reasonably control the amount of fuel supply necessary to generate an acceleration torque.
There is a problem that this control must be done by every driver himself as things stand today. That is, it is necessary to educate every driver so as to gently step an accelerator pedal until an aimed vehicle speed is achieved. That is, it is necessary to educate every driver so as not to fully step down an accelerator pedal and release the accelerator pedal after the aimed speed is achieved.
The present inventors have investigated whether the above mentioned problem can be solved by improving the conventional auto-cruising device. That is, it has been investigated whether or not the amount of fuel supply can be controlled such that the acceleration of the vehicle is controlled at a reasonable acceleration even when a driver fully steps down an accelerator pedal rapidly to accelerate a vehicle, unlike the conventional control manner in which the amount of fuel supplied to an engine of the vehicle is directly corresponding to the stepping amount of the accelerator pedal. The conventional auto-cruising device constructed such that the cruising control is actuated manually by the driver becomes meaningless unless the operator actuates the auto-cruising control. However, if the control of the auto-cruising device is automatically actuated simultaneously with a start of an engine of a vehicle in a parking state and the above control for gently increasing an actual fuel flow rate is performed even when the accelerator pedal is fully stepped down by the driver, a starting performance of the vehicle may be degraded.